Mechanical Engineering Commons^™

Performance Optimization Of Multi-Core Processors Using Core Hopping - Thermal And Structural, Sunil Lingampalli

Mechanical and Aerospace Engineering Theses - Archive

As the work load on the single core processor increases, it's processing speed increases resulting in increased power densities and die temperatures. The increase in die temperature results in decreased performance and reliability and increased leakage currents and cooling costs. In order to decrease the work load and the cooling cost on the single core processor, multi-core processors have been implemented. Multicore Processors also known as Chip Multi Processors (CMP's) are the processors which contain two or more independent cores on a chip. In CMPs, if one core reaches its critical temperature, the workload is transferred to the other. This …

Estimation Of Aircraft States And Wind Exposure In Aerial Refueling, Je Hyeon Lee

Mechanical and Aerospace Engineering Dissertations - Archive

When a tanker and receiver aircraft fly in tight formation in an aerial refueling operation, they are exposed to various sources of wind with varying magnitude and direction. The tanker and the receiver aircraft experience prevailing wind and turbulence. The receiver aircraft is also subject to an additional wind field induced by the wake of the tanker.The receiver aircraft is required to fly in a precise trajectory relative to the tanker. Especially, the receiver aircraft should stay at a position with small tolerances for the fuel transfer operation while the tanker aircraft flies straight level and makes constant altitude turns. …

Atomic Friction Studied By Modeling The Buried Inteface, Yalin Dong, Ashlie Martini, Qunyang Li, Robert W. Carpick

Mechanical Engineering Faculty Research

Molecular dynamics simulation is carried out to model the single-asperity friction in atomic force microscope experiments. Superlubricity is achieved through misalignment between the AFM tip and substrate. Direct observation of the buried interface reveals that incommensurability-induced inhomogeneous shear stress can cause ultra-low atomic scale friction.

A New Look At Optimum Design For Convecting-Radiating Annular Fins Of Trapezoidal Profile, Benjamin T.F. Chung

Mechanical Engineering Faculty Research

This paper deals with a controversial problem in answering the question “Does the optimum fin design always exist? If not, what are the optimization ranges and limitations?” These authors employ a general example of convecting-radiating trapezoidal annular fin with heat transfer at the tip and wall resistance at the interface. The present results indicate that the answer to the above first question is negative. The ranges of fin optimum design under different thermal and physical conditions are proposed. The effects of Biot number, radiation number, the heat loss at the tip, fin profile and overall wall resistance on fin optimization …

Fabrication Of Micropatterns On 3d Surfaces And Generation Of Linked Zno Nanowires, Hui Wang

Mechanical and Aerospace Engineering Dissertations - Archive

Conventional lithographic approaches are good at fabricating structures on the top surfaces of substrates. They are not suited for 3D surface patterning due to the fact that vertical radiation exposure is employed to transfer patterns. In the meanwhile, patterns generated on 3D surfaces, such as the vertical sidewalls of silicon channels and the irregular surfaces of glass micropipettes may provide valuable applications in microfluidics, 3D circuits, bioengineering and so on. In this work, we developed new approaches to produce metal micropatterns on the vertical sidewalls of silicon channels as well as to fabricate two separated metal microlines on the tips …

Development Of An Experimental And Analytical Model Of An Active Cooling Method For High-Power Three-Dimensional Integrated Circuit (3d-Ic) Utilizing A Multidimensional Configured Thermoelectric Modules, Huy Phan

Mechanical and Aerospace Engineering Dissertations - Archive

An increase in demand for more functionality and capacity of microelectronic components within the same logistic footprint drives the growth of three-dimensional integrated circuit (3D-IC) packaging technologies in recent years. However, the reduction in size and an increase in transistors density also intensified the heat flux of stacked-dice, which introduces many thermal challenges at both the package and cooling levels. Traditional passive cooling system such as forced air convection cooling, phase change materials and passive or active heat sinks will become inadequate to cool future processors and cannot accommodate the demand of future sub-ambient cooling of 3D-ICs. Within the past …

Hybrid Dynamic Simulation For Performance Optimization Of Legged Mechanisms, Daniel Montrallo Flickinger

Mechanical and Aerospace Engineering Dissertations - Archive

Agile locomotion is needed for mobile robots to efficiently navigate challenging terrain. The ability of an agile legged mobile robot to abruptly change trajectory allows it toquickly react to obstacles and successfully operate in environments usually more suited forlegged animals. The research presented herein aims to increase the agility and performanceof legged robots.Using hybrid dynamic simulation, novel methods are developed to model the inter-action of a legged robot with the ground. In considering robot agility, an accurate model ofthe events that occur while in contact is needed. Methods are developed to model groundinteraction where oblique angled impacts occur, and to …

Design And Modeling Techniques For Cooling Of Telecommunication Systems, Naveen Kannan

Mechanical and Aerospace Engineering Theses - Archive

Conventional data centers are extremely large buildings that have complex power distribution and cooling systems. These traditional brick and mortar data centers employ relatively expensive cooling systems and are inefficient. It has in turn led to an increase in construction and operational costs. These inefficiencies of traditional data centers can be overcome by partitioning the server load into modular sections which can be deployed, powered and cooled depending on availability and requirement. Furthermore, improvements in efficiency and operational costs can be achieved by employing "free cooling" to cool the IT equipment. Free cooling involves the introduction of outside air through …

Design Optimization Of A Wind Turbine Blade, Bharath Koratagere Srinivasa Raju

Mechanical and Aerospace Engineering Theses - Archive

This work focuses on designing a blade of 45 meters in length that produces a power of 1.6 MW. The design of the blade was done using the Blade Element Momentum theory and the Prandtl's tip loss factor was used. The aerodynamic loads and differential power at are tabulated and plotted.The finite element method for analysis of the blade is used. As the chord lengths vary decreasingly along the blade radii in order to use the simple beam theory the breath and height of the blade is considered as a function of the chord length, hence the analysis is done …

Filling Of Methane/Air Mixture In A Tube For Pulse Detonation Engines, Shravani Dwarakapally

Mechanical and Aerospace Engineering Theses - Archive

In pulse detonation engines, filling is a time consuming process; reducing these times will help to increase the frequency. The filling of a detonation tube, 1 m long tube with an internal diameter of 101.6 mm, closed at one end and opened at the other, was studied using the unsteady flow solver methane and air nominally at STP· Three cases were examined: (i) a 25.4 mm diameter port at the center of the closed end, (ii) nine ports of 25.4 mm diameter, one at the center of the closed end and eight distributed in two diametrically opposite rows, equally, four …

Control Of Airship Motion In The Presence Of Wind, Jatuporn Nakpiam

Mechanical and Aerospace Engineering Theses - Archive

This research effort develops a guidance and control system for a small airship to fly through assigned waypoints in the three dimensional space with a desired speed in the presence of wind and wind gust. In the control system development and validation, a simulation environment based on the nonlinear 6-DOF model of an airship, including the effect of the wind, is used. The airship has five control variables, the main thrust, the main thrust angle, the tail thrust, elevator and rudder deflections. The effectiveness of the elevator and rudder degrades as the speed of the airship decreases. The controller design …

Using Thermally Coupled Reactive Distillation Columns In Biodiesel Production, Nghi Nguyen, Yaşar Demirel

Yaşar Demirel Publications

Production of ethyl dodecanoate (biodiesel) using lauric acid and methanol with a solid acid catalyst of sulfated zirconia is studied by using two distillation sequences. In the first sequence, the methanol recovery column follows the reactive distillation column. In the second sequence, the reactive distillation and methanol recovery columns are thermally coupled. Thermally coupled distillation sequences may consume less energy by allowing interconnecting vapor and liquid streams between the two columns to elminate reboiler or condenser or both. Here we study the thermally coupled side-stripper reactive distillation and eliminate the condenser of the reactive distillation column. Both the sequences are …

Multi-Sensor Optimization Of The Simultaneous Turning And Boring Operation, Erick Johan Deane

Electronic Theses and Dissertations

To remain competitive in today’s demanding economy, there is an increasing demand for improved productivity and scrap reduction in manufacturing. Traditional manufacturing metal removal processes such as turning and boring are still one of the most used techniques for fabricating metal products. Although the essential metal removal process is the same, new advances in technology have led to improvements in the monitoring of the process allowing for reduction of power consumption, tool wear, and total cost of production. Replacing used CNC lathes from the 1980’s in a manufacturing facility may prove costly, thus finding a method to modernize the lathes …

Study Of High Efficiency Micro Thermoelectric Energy Harvesters, Steven Michael Pedrosa

Electronic Theses and Dissertations

Thermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat sources, and convert the captured heat into usable electricity. The operating principle of a thermoelectric device requires that a temperature gradient be present across the device, which induces the flow of electrons from …

Investigation Into The Potential Use Of Windbreaks To Improve Solar Collector Performance, Michael Watts

All Graduate Theses, Dissertations, and Other Capstone Projects

The global demand for energy is ever increasing; however, the world has a limited number of fossil fuels available. Therefore, alternative renewable energy sources must be utilized. For this reason, solar thermal collectors have become an increasingly popular method for providing hot water or space heating. However, solar thermal collectors are most commonly used in areas that experience warm climates throughout the year. In areas that experience seasonal climates, the cold temperatures and harsh climate conditions significantly reduce the performance of solar thermal collectors during the winter months. This thesis examined the potential that the implementation of a windbreak could …

Autonomous Mobility And Manipulation Of A 9-Dof Wmra, William Garrett Pence

USF Tampa Graduate Theses and Dissertations

The wheelchair-mounted robotic arm (WMRA) is a 9-degree of freedom (DoF) assistive system that consists of a 2-DoF modified commercial power wheelchair and a custom 7-DoF robotic arm. Kinematics and control methodology for the 9-DoF system that combine mobility and manipulation have been previously developed and implemented. This combined control allows the wheelchair and robotic arm to follow a single trajectory based on weighted optimizations. However, for the execution of activities of daily living (ADL) in the real-world environment, modified control techniques have been implemented.

In order to execute macro ADL tasks, such as a "go to and pick up" …

Low-Cost Prosthetic Leg For The Vida Nueva Prosthesis Clinic, Sarah M. Baker, Justin G. Lekos, Jen Van Donk, Kevin Yamauchi

Mechanical Engineering

The Piernas de Vida team partnered with the Vida Nueva Clinic of Prostheses and Orthoses in Choluteca, Honduras to design, plan, and implement a prosthetic foot that could be manufactured entirely by the technicians at the clinic in order to reduce their costs and ultimately allow them to serve more patients each year. Currently, the clinic uses a prefabricated prosthetic lower limb provided by the International Committee of the Red Cross (ICRC) which can be adapted to both transDfemoral and transDtibial patients. The team has successfully developed a foot, currently called the Layer Foot, which can be used by the …

Development Of A Heat Transfer Test Rig For Finding Heat Transfer Characteristics Of Liquid Methane, Sergio Flores

Open Access Theses & Dissertations

Most large scale rocket engines use a regeneratively cooled system to cool the rocket engine using either the rocket fuel or oxidizer. The use of liquid methane as a rocket fuel is an emerging technology proving to have several advantages over current rocket fuels. However, liquid methane is lacking the extensive research as a rocket fuel compared to highly used rocket fuels like liquid hydrogen. A heat transfer test rig was built with the goal to characterize the heat transfer characteristics of liquid methane as it passes through a heated channel. The development of the test rig underwent considerations designed …

Improved Joining Method For Segmental Prestressed Structures, Ralph Warren Jensen

Open Access Theses & Dissertations

This dissertation addresses the need for more robust and materially efficient structures, specifically structures that absorb higher levels of energy, can self-erect and which have variable reaction capabilities. These structures can take much higher levels of strain and loading compared to current technologies in reinforced concrete and carbon fiber composites. These structures are made using a novel method of joining segmental elements. A great advantage with this segmental structural system is it's survivability under overloaded conditions. During an impact, or concentrated pressure load, the structure will wrap around the impact zone thereby widely distributing the contact stresses. This function or …

Phase Change Materials As A Thermal Storage Device For Passive Houses, Kevin Ryan Campbell

Dissertations and Theses

This study describes a simulation-based approach for informing the incorporation of Phase Change Materials (PCMs) in buildings designed to the "Passive House" standard. PCMs provide a minimally invasive method of adding thermal mass to a building, thus mitigating overheating events. Phase change transition temperature, quantity, and location of PCM were all considered while incrementally adding PCM to Passive House simulation models in multiple climate zones across the United States. Whole building energy simulations were performed using EnergyPlus from the US Department of Energy. A prototypical Passive House with a 1500 Watt electric heater and no mechanical cooling was modeled. The …